package com.sfx.concurrent.demo.concurrent.ConnectionPool;

import lombok.extern.slf4j.Slf4j;

import java.sql.*;
import java.util.Map;
import java.util.Properties;
import java.util.Random;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicIntegerArray;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: sfx
 * Date: 2023-01-21
 * Time: 17:41
 */

class Test {
    public static void main(String[] args) {
        MyConnectionPool myConnectionPool = new MyConnectionPool(2);
        for(int i =0;i<5;++i) {
            new Thread(()->{
                Connection con = myConnectionPool.borrow();
                try {
                    Thread.sleep(new Random().nextInt(1000));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                myConnectionPool.free(con);
            },"线程"+i).start();
        }
    }
}

@Slf4j(topic = "c.MyConnectionPool")
public class MyConnectionPool {

    //连接池的大小
    private final int poolSize;
    //标记连接池中每一个连接的状态
    private AtomicIntegerArray states;
    //创建连接池数组(预留好连接)
    private Connection[] connections;

    //初始化连接池
    public MyConnectionPool(int poolSize) {
        this.poolSize = poolSize;
        this.states = new AtomicIntegerArray(new int[poolSize]);
        this.connections = new Connection[poolSize];
        for(int i =0;i<poolSize;++i) {
            connections[i] = new MockConnection("connection : " + (i+1));
        }
    }

    //借连接
    public Connection borrow() {
        //不断尝试获取未占用连接
        while(true) {
            //遍历连接状态,看哪一个连接是空闲状态,从而返回该连接,让线程使用
            for(int i =0;i<this.poolSize;++i) {
                if (this.states.get(i)==0) {//当前连接未占用
                    //将该连接标记为使用状态
                    if (states.compareAndSet(i,0,1)) {//存在线程安全问题,使用CAS,
                        // 有可能多个线程同时获取该连接,会导致多个线程使用这一个连接
                        //如果CAS成功,返回该连接
                        log.debug("borrow{}",connections[i]);
                        return connections[i];
                    }
                }
            }
            //如果没有空闲连接,就一直等待有空闲连接
            synchronized (this) {
                try {
                    log.debug("wait...");
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //还连接(每一个线程都对应着自己的一个连接,所以不会出现线程安全问题)
    public void free(Connection conn) {
        //遍历连接数组
        for(int i =0;i<this.poolSize;++i) {
            if(connections[i]==conn) {
                //如果有该连接,对其释放
                states.set(i,0);
                //同时唤醒等待的线程,告诉有连接可用了
                synchronized (this){
                    log.debug("free{}",conn);
                    this.notifyAll();
                }
                break;
            }
        }
    }
}

class MockConnection implements Connection {
    private String name;

    public MockConnection(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "MockConnection{" +
                "name='" + name + '\'' +
                '}';
    }

    @Override
    public Statement createStatement() throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql) throws SQLException {
        return null;
    }

    @Override
    public String nativeSQL(String sql) throws SQLException {
        return null;
    }

    @Override
    public void setAutoCommit(boolean autoCommit) throws SQLException {

    }

    @Override
    public boolean getAutoCommit() throws SQLException {
        return false;
    }

    @Override
    public void commit() throws SQLException {

    }

    @Override
    public void rollback() throws SQLException {

    }

    @Override
    public void close() throws SQLException {

    }

    @Override
    public boolean isClosed() throws SQLException {
        return false;
    }

    @Override
    public DatabaseMetaData getMetaData() throws SQLException {
        return null;
    }

    @Override
    public void setReadOnly(boolean readOnly) throws SQLException {

    }

    @Override
    public boolean isReadOnly() throws SQLException {
        return false;
    }

    @Override
    public void setCatalog(String catalog) throws SQLException {

    }

    @Override
    public String getCatalog() throws SQLException {
        return null;
    }

    @Override
    public void setTransactionIsolation(int level) throws SQLException {

    }

    @Override
    public int getTransactionIsolation() throws SQLException {
        return 0;
    }

    @Override
    public SQLWarning getWarnings() throws SQLException {
        return null;
    }

    @Override
    public void clearWarnings() throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public Map<String, Class<?>> getTypeMap() throws SQLException {
        return null;
    }

    @Override
    public void setTypeMap(Map<String, Class<?>> map) throws SQLException {

    }

    @Override
    public void setHoldability(int holdability) throws SQLException {

    }

    @Override
    public int getHoldability() throws SQLException {
        return 0;
    }

    @Override
    public Savepoint setSavepoint() throws SQLException {
        return null;
    }

    @Override
    public Savepoint setSavepoint(String name) throws SQLException {
        return null;
    }

    @Override
    public void rollback(Savepoint savepoint) throws SQLException {

    }

    @Override
    public void releaseSavepoint(Savepoint savepoint) throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
        return null;
    }

    @Override
    public Clob createClob() throws SQLException {
        return null;
    }

    @Override
    public Blob createBlob() throws SQLException {
        return null;
    }

    @Override
    public NClob createNClob() throws SQLException {
        return null;
    }

    @Override
    public SQLXML createSQLXML() throws SQLException {
        return null;
    }

    @Override
    public boolean isValid(int timeout) throws SQLException {
        return false;
    }

    @Override
    public void setClientInfo(String name, String value) throws SQLClientInfoException {

    }

    @Override
    public void setClientInfo(Properties properties) throws SQLClientInfoException {

    }

    @Override
    public String getClientInfo(String name) throws SQLException {
        return null;
    }

    @Override
    public Properties getClientInfo() throws SQLException {
        return null;
    }

    @Override
    public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
        return null;
    }

    @Override
    public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
        return null;
    }

    @Override
    public void setSchema(String schema) throws SQLException {

    }

    @Override
    public String getSchema() throws SQLException {
        return null;
    }

    @Override
    public void abort(Executor executor) throws SQLException {

    }

    @Override
    public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {

    }

    @Override
    public int getNetworkTimeout() throws SQLException {
        return 0;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }
}